It is well known that the practice of Reflectometry, Spectrophotometry, Ellipsometry, Polarimetery and the like requires directing electromagnetic beams at samples at known angles (AOI) and planes (POI) of incidence. Typical practice is to set an angle (AOI) and/or plane (POI) of incidence by the directing of an electromagnetic beam and/or the orienting of a sample such that the desired angular relationships are achieved. This can be tedious and requiring of relatively expensive equipment, where high precision is desired. However precise knowledge of the (AOI) and/or (POI) are necessary for achieving accurate analysis of sample characterizing data, and errors between intended and actually achieved (AOI) and/or (POI) lead to errors in analysis.
While present invention systems can be applied in any material system investigation system such as Reflectometer, Spectrophotometer, Polarimeter and the like Systems, an important application is in Ellipsometer Systems, whether Monochromatic or Spectroscopic. It should therefore be understood that Ellipsometry involves acquisition of sample system characterizing data at single or at multiple Wavelengths, and at one or more Angle(s)-of-Incidence (AOI) of a Beam of Electromagnetic Radiation to a surface of the sample system. Ellipsometry is generally well described in a great many number of publications, one such publication being a review paper by Collins, titled “Automatic Rotating Element Ellipsometers: Calibration, Operation and Real-Time Applications”, Rev. Sci. Instrum, 61(8) (1990).
A typical goal in ellipsometry is to obtain, for each wavelength in, and angle of incidence of said beam of electromagnetic radiation caused to interact with a sample system, sample system characterizing PSI and DELTA values, (where PSI is related to a change in a ratio of magnitudes of orthogonal components rp/rs in said beam of electromagnetic radiation, and wherein DELTA is related to a phase shift entered between said orthogonal components rp and rs, caused by interaction with said sample system:ρ=rp/rs=Tan(Ψ) exp(iΔ)
Continuing, Ellipsometer Systems generally include a source of a beam of electromagnetic radiation, a Polarizer, which serves to impose a known, (typically linear), state of polarization on a beam of electromagnetic radiation, a Stage for supporting a sample system, and an Analyzer which serves to select a polarization state in a beam of electromagnetic radiation after it has interacted with a sample system, and pass it to a Detector System for analysis therein. As well, one or more Compensator(s) can be present and serve to affect a phase retardance between orthogonal components of a polarized beam of electromagnetic radiation. A number of types of ellipsometer systems exist, such as those which include rotating elements and those which include modulation elements. Those including rotating elements include Rotating Polarizer (RP), Rotating Analyzer (RA) and Rotating Compensator (RC). While not limiting, a preferred embodiment is Rotating Compensator (RC) Ellipsometer Systems because they do not demonstrate “Dead-Spots” where obtaining ellipsometric data is difficult. They can read PSI and DELTA of a Material System over a full Range of Degrees with the only limitation being that if PSI becomes essentially zero (0.0), one can't then determine DELTA as there is not sufficient PSI Polar Vector Length to form the angle between the PSI Vector and an “X” axis. In comparison, Rotating Analyzer and Rotating Polarizer Ellipsometers have “Dead Spots” at DELTA's near 0.0 or 180 Degrees and Modulation Element Ellipsometers also have a “Dead Spot” at PSI near 45 Degrees). The utility of Rotating Compensator Ellipsometer Systems should then be apparent. Another benefit provided by Rotating Compensator Ellipsometer Systems is that the Polarizer (P) and Analyzer (A) positions are fixed during data acquisition, and that provides benefit in that polarization state sensitivity to input and output optics during data acquisition is essentially non-existent. This enables relatively easy use of optic fibers, mirrors, lenses etc. for input/output. For insight it is noted that a Patent to Johs, U.S. Pat. No. 5,872,630 describes a material system investigation system comprising a source of a polychromatic beam of electromagnetic radiation, a polarizer, a stage for supporting a sample system, an analyzer, a dispersive optics and at least one detector system which contains a multiplicity of detector elements, said material system investigation system optionally comprising at least one compensator(s) positioned at a location selected from the group consisting of:                before said stage for supporting a sample system, and        after said stage for supporting a sample system, and        both before and after said stage for supporting a sample system;such that when said material system investigation system is used to investigate a sample system present on said stage for supporting a sample system, at least one of said compensator(s) is/are caused to continuously rotate while a polychromatic beam of electromagnetic radiation produced by said source of a polychromatic beam of electromagnetic radiation is caused to pass through said polarizer and said compensator(s), said polychromatic beam of electromagnetic radiation being also caused to interact with said sample system, pass through said analyzer and interact with said dispersive optics such that a multiplicity of essentially single wavelengths are caused to simultaneously enter a corresponding multiplicity of detector elements in said at least one detector system. Said U.S. Pat. No. 5,872,630 Patent to Johs is also disclosed as it shows use of a Beam Splitter to direct electromagnetic radiation into a Multi-element Alignment Detector (CH).        
A Patent to Woollam et al, U.S. Pat. No. 5,582,646 is disclosed as it describes obtaining ellipsometric data through windows in a vacuum chamber, utilizing other than a Brewster Angle of Incidence and analysis of data in sensitive wavelength regions to enhance sensitivity.
Patent to Woollam et al, U.S. Pat. No. 5,373,359 is identified as it shows the presence of a Multi-Element Detector (24) applied to beam alignment in an Ellipsometer System.
Patent to Johs et al. U.S. Pat. No. 5,666,201 and Patent to Green et al., U.S. Pat. No. 5,521,706, and Patent to Johs et al., U.S. Pat. No. 5,504,582 are disclosed for general information as they pertain to Rotating Analyzer ellipsometer systems.
Patent to Bernoux et al., U.S. Pat. No. 5,329,357 is identified as it describes the use of optical fibers as input and output means in an ellipsometer system.
A Patent to Berger et al., U.S. Pat. No. 5,343,293 describes an Ellipsometer which comprises means to direct an electromagnetic beam onto a sample system.
A Patent to Canino, U.S. Pat. No. 4,672,196 describes a system which allows rotating a sample system to control the angle of incidence of a beam of electromagnetic radiation thereonto. Multiple detectors are present to receive the resulting reflected beams.
A Patent to Biork et al., U.S. Pat. No. 4,647,207 describes an ellipsometer system in which reflecting elements are moved into the path of a beam of electromagnetic radiation.
U.S. Pat. No. 5,412,473 to Rosencwaig et al., describes a ellipsometer system which simultaneously provides an electromagnetic beam at a sample surface at numerous angles of incidence thereto.
A European Patent, No. EP 1 034 413 B1 is disclosed as it describes a system for determining an angle of reflection an electromagnetic beam from a sample in an ellipsometer.
Even in view of the prior art, need remains a relatively inexpensive system and methodology which allows easily substantially setting desired (AOI) and/or (POI), wherein said system and method further enable detection of errors between intended and achieved (AOI) and/or (POI), said methodology then providing for correction of said errors during analysis of data acquired at actually realized, as opposed to intended (AOI) and (POI) settings.